Collection Mapping

Suppose I have the following classes:

class A1 {
  List<B1> bList;
}

class B1 {
  Long id;
}

---

class A2 {
  List<Long> bList;
}

I want to map class A1 to A2 with Dozer, where A1.bList contains B1 objects and A2.bList contains only the IDs of the B1 objects.

How woul开发者_开发技巧d the mapping look like?

Thank you.

I think you could try setting up a mapping for Long to B1. If I remember rightly this only works one way, I can't remember which way tho. Sorry, hope this helps.

You can use a dozer custom converter. Dozer customer converter

An example: (possible errors, didn't compile or test it)

<mapping>
  <class-a>A1</class-a>
  <class-b>A2</class-b>    
  <field custom-converter="converters.YourCustomConverter">
    <a>bList</a>
    <b>bList</b>
  </field>
</mapping>

The custom converter:

public class YourCustomConverter implements CustomConverter {

    public Object convert(Object destination, Object source, Class destClass, Class sourceClass) {
        if (source == null) {
            return null;
        }
        if (source instanceof List<?>) {
            List<?> list = ((List<?>) source);
            if (list.isEmpty()) {
                return null;
            }
            if (list.get(0) instanceof B1) {
                List<Long> longList = new ArrayList<Long>();
                for (B1 b1 : list) {
                    longList.add(b1.getId());
                }
                return longList;
            } else (list.get(0) instanceof Long) {
                // do the inverse of the above
            } else {
                throw new MappingException("Wrong type ...");
            }
        } else {
            throw new MappingException("Converter YourCustomConverter used incorrectly. Arguments passed in were:"
                    + destination + " and " + source);
        }
    } 
}

I think you can do this by overridding toString() method in B1 and it would work.

Here's sample code:

@Override
public String toString() {
return new String(this.id);
}

And in your mapping do the following changes:

<field>
 <a>bList</a>
 <b>bList</b>
 <a-hint>B</a-hint>
 <b-hint>java.lang.Long<b-hint>
</field>  

So,when dozer tries to bind B1, it will return its id as String and then dozer will perform an automatic conversion between String and Long.